While it's a very interesting thing to know, I wouldn't say that it answers any questions about current usage. No one I believe argues that "been" has it's historical roots the same as "go", so explaining how it came to pass that "been to" is used this way doesn't seem relevant to the discussion (although it was the most interesting part of it to me).
What seems more important to me is that all native speakers here (and now) think "been" is not the past participle of "go".
Unfortunately, with the OALD, CALD, Quirk at al, Leech and Swan all saying that
been is the past participle of GO in the constructions we are talking about, some people might assume that this must be true. Such people would overlook the fact that the authorities named have presented no justification for their assertion, while we have presented some arguments for our belief that it is not.
If we could produce evidence of
BE + to + place used in the past in other tenses than the present perfect, then it would show beyond any shadow of doubt that the assertions of Quirk and the others are wrong.
It's not vitally important - so long as learners
use the forms correctly, it doesn't really matter what they believe. I just happen to object very strongly to incorrect 'facts' being presented in discussions of English. I
know that
been is not ever the past participle of GO. I would like to be able to convince the unbelievers of this.